Re: THREADED_DELTA_SEARCH

[Nicolas Pitre <nico@cam.org>]

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On Thu, 10 Jul 2008, Junio C Hamano wrote:

> Pierre Habouzit <madcoder@debian.org> writes:
> 
> >   I'm using it in production for quite a long time now, and I wonder if
> > there is any specific reason why it's not default. Debian activated it
> > by default too a couple of weeks ago, which means that it's in
> > production on quite a large scale, and there are no issues reported
> > either. Would a patch making it default be accepted ? It's quite handy
> > given that SMP machines are really pervasive nowadays…
> 
> There were two issues, IIRC.
> 
>  (1) resulting pack could be suboptimal, due to delta-chain getting cut
>      betweeen the worker thread boundary.
> 
>  (2) exploding memory use, suspected to be due to malloc pool
>      fragmentation under multithreading.
> 
> The former was only an issue with early iterations of the code and the
> current code has much improved behaviour on this point,

I would say it is even negligible.

> but I do not
> recall the latter issue has been addressed.

Well, for "standard" repositories such as the Linux kernel, things 
always worked just fine.  And commit eac12e2d is apparently helping a 
lot with the remaining odd cases.  And if someone has problems due to 
this then a simple 'git config --global pack.threads 1' would restore 
the non threaded behavior.


Nicolas